One-hundred thirty-one prominent Republicans have now signed an amicus brief urging the Supreme Court to rule that gay couples have a constitutional right to marry. The importance of the news has been generally downplayed: conservative activists dismiss the brief as the work of a moderate minority in the GOP, while others contend that as most of the signers are not current officeholders, their participation does not represent a real shift in party ideology. Both critiques are valid. But the signing of the brief by so many Republican leaders should prove to be a seminal moment nonetheless in both the history of the party and the gay rights movement, as it marks a welcome deviation from traditional conservative orthodoxy.

To be sure, support for gay marriage remains a minority opinion in the Republican Party. A national Gallup poll conducted in November 2012 found that only 30% of Republicans believe marriage between same-sex couples should be legal. But that number is up from 20% in 2009 – in other words, views are shifting.

As PolicyMic writer Roy Klabin points out, the amicus brief "could theoretically be the first signal flare of a battle for the party’s future."

Of course, Klabin also observes that "A more cynical take would note that because almost all the signers are out of office, they have no political capital to lose by challenging Boehner and the Republican leadership." Yes, only two sitting GOP members of Congress, Richard Hanna of New York and Ileana Ros-Lehtinen of Florida, signed the brief. But the list of signers also includes overlooked current elected officials at the state level, including legislators from New Hampshire, New York, and ruby-red Wyoming. (It is worth noting that it in New York, four Republican state senators provided the deciding votes to make gay marriage legal in 2011.) Furthermore, several signers – including once-and-future presidential contender Jon Huntsman and recently defeated House Representatives Mary Bono Mack and Charles Bass – could run for office in the future but decided to risk political backlash and attach their names to the document nonetheless.

Republican support for gay marriage is thus not a fluke or a passing fad. The fact is the sheer number of prominent leaders who have signed on to the brief would have been unimaginable even just a few years ago. The last successful Republican candidate for president, George W. Bush, actually made opposition to gay marriage central to his campaign in 2004. Vice President Dick Cheney was a notable dissenter at the time, declaring when pressed on the issue that “my general view is that freedom means freedom for everyone.” But his was a lonely voice and conservatives largely dismissed it as an aberration, a case of he-supports-gay-marriage-because-his-daughter-is-gay. Clearly, the party has changed significantly since then.

Unsurprisingly, discussion of the amicus brief has focused on political calculations, with Eric Sasson of The New Republic opining that “opposing gay rights is no longer a winning issue for the party.” After all, the aforementioned November 2012 Gallup poll found that 53% of Americans and 73% of young voters, those aged 18-29, favor the legalization of gay marriage. Nevertheless, the brief is welcome news not only because it potentially furthers the Republican Party’s competitiveness, but also primarily because gay marriage deserves conservative support, plain and simple. As David Frum, Jon Huntsman, and Meg Whitman all detail in their explanations for signing the brief, supporting gay marriage is firmly in line with the conservative desire for greater liberty, personal responsibility, and strong family units, and the economic and societal benefits that come with each. “I don't support gay marriage despite being a Conservative,” United Kingdom Prime Minister David Cameron noted in 2011. “I support gay marriage because I'm a Conservative.”

Ultimately, Americans will have to wait until March 26 to see what impact the amicus brief will have, if any, on the state of marriage in the United States. That date is when oral argument for Hollingworth v. Perry, the lawsuit supported by the brief, is scheduled. Leading the argument for the plaintiffs on that day will be no less a Republican than Theodore Olson, solicitor general under President W. Bush, who ably outlined the conservative case for gay marriage from a constitutional standpoint for Newsweek in 2010; “it is,” he wrote, “the last major civil-rights milestone yet to be surpassed in our two-century struggle to attain the goals we set for this nation at its formation.”

But regardless of the outcome of the case, the brief is significant for demonstrating that contrary to the misconception of a close-minded, never-changing party, there are Republicans who welcome the debate on gay marriage legalization. While pro-gay marriage Republicans were once just a few lonely voices in the political wilderness, they are now a strengthening party faction. In that sense, the brief marks a coming out of sorts for the Grand Old Party.